1. Field of the Invention
The present invention relates to a driver circuit and the method thereof, and more particularly, to an LED driver circuit and the method thereof.
2. Description of the Related Art
Compared to most conventional light emitting devices, LEDs consume less power, have longer lifetime and are more durable. Therefore, most indicator devices nowadays, such as traffic signs and commercial billboards, are implemented by LEDs. However, since a large number of those large indicator devices are placed outdoors, there are various sources of hazard, such as weather, animals colliding with them, or even droppings, that can damage such LED indicator devices. Unfortunately, conventional LED indicator devices seldom exhibit fault detection mechanism. Therefore, when LED indicator device are damaged, the control device, such as a control-end processor, has no knowledge of the location and the number of the damaged LEDs, and only by human eyes can such information be observed. Since the height of many modern LED indicator devices are over tens of meters, it requires maintenance personnel to climb up high to confirm information on the damaged LED indicator device, which is an arduous task and costs a lot of money.
To solve the problems mentioned above, a fault detection mechanism can be designed for those LED indicator devices such that a control device is able to obtain the fault information of the damaged LEDs automatically. FIG. 1 shows a conventional LED driver circuit 100, which is connected to a control-end processor 200 and serves as the driver for a plurality of LEDs 400. The LED driver circuit 100 comprises a shift register 110, a plurality of latches 120, a plurality of driver units 130, a plurality of comparators 140, a plurality of state registers 150 and a state switching circuit 160, wherein the number of the flip-flops in the shift register 110, the number of the plurality of latches 120, the number of the plurality of driver units 130 and the number of the plurality of LEDs 400 are the same. The input signals of the LED driver circuit 100 include an input data, a latch signal, a switch signal and a clock signal. The output signal of the LED driver circuit 100 includes an output data. The input terminal of the LED driver circuit 100 for the input data is connected to the first flip-flop of the shift register 110. The output terminal of the LED driver circuit 100 for the output data is connected to the last flip-flop of the shift register 110.
The state switching circuit 160 determines the status of the LED driver circuit 100 according to the latch signal and the switch signal. When in a display mode, the LED driver circuit 100 receives display signals from the control-end processor 200. The received display signals are then serially stored in the shift register 110. When the storing process of the display signals is completed, the data stored in the shift register 110 is then outputted to and stored in the plurality of latches 120. The output terminals of the plurality of latches 120 are connected to the plurality of driver units 130 respectively. The plurality of driver units 130 have their output terminals connected to, and accordingly drive, the plurality of LEDs 400.
When in a debug mode, the LED driver circuit 100 receives fault-detecting signals (such as the signals of which the bits are all 0s or all 1s) from the control-end processor 200. The received fault-detecting signals are then serially stored in the shift register 110. When the storing process of the fault-detecting signals is complete, the data stored in the shift register 110 is then outputted to and stored in the plurality of latches 120 so as to be the input signal for the plurality of driver units 130. The input terminals of the plurality of comparators 140 are respectively connected to the output terminals of the plurality of LEDs 400 and a reference voltage. The output signals of the comparators 140 indicate whether the plurality of LEDs 400 are in fault state. The plurality of state registers 150 store the comparison results of the plurality of comparators 140, and then stores such results to the shift register 110 at a later time such that the results can be outputted and transmitted back to the control-end processor 200. The control-end processor 200 obtains the fault information of the plurality of LEDs 400 according to the comparison results. For instance, if the fault-detecting signal is a signal of which the bits are all 1s, which should turn on all the plurality of LEDs 400, and the comparison results contain bits of “0”, then the control-end processor 200 determines that the LEDs 400 at the corresponding locations are faulty.
FIG. 2 shows the waveforms of the input and output signals of the LED driver circuit 100. As shown in FIG. 2, the clock signal controls the input operation of the shift register 110. When in the display mode, the display signals are serially stored into the shift register 110. At such point, the output signals of the LED driver circuit 100 are redundant data. When the storing process of the display signals is complete, a pulse of the latch signal triggers the data stored in the shift register 110 to be stored into the plurality of latches 120. The switch signal then switches to low to activate the plurality of driver units 130, and the plurality of LEDs 400 are driven thereby according to the data stored in the plurality of latches 120. At such point, the output signal is the display signals. After the state switching circuit 160 switches the mode of the LED driver circuit 100 to the debug mode, the driver circuit 100 is ready for the fault detection of the plurality of LEDs, or is ready to transmit the data stored in the plurality of state registers 150 back to the control-end processor 200. At such point, the output signal is the fault information. As shown in FIG. 2, the modes of the driver circuit 100 further include an exit mode, which serves as an interfacing mode between the display mode and the debug mode.
However, the aforesaid prior art needs to be switched between several modes, which heavily increases the control complexity for the control-end processor 200. Moreover, the addition of the plurality of state registers 150 and the state switching circuit 160 increases the hardware cost. Therefore, there is a need to design a display mechanism, which not only can detect the fault status of the plurality of LEDs synchronously, but also does not increase the hardware cost.